<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button id="btn">发消息</button>
  <button id="btn2">关闭连接</button>
  <script>
    // 通过 websocket 完成前后端通信
    // 1. 建立连接
    const ws = new WebSocket('wss://javascript.info/article/websocket/demo/hello')
    // 2. 监听连接成功
    ws.onopen = () => {
      console.log('连接成功')
    }
    // 3. 如何发消息
    document.querySelector('#btn').addEventListener('click', () => {
      ws.send('你好 websocket 服务器')
    })
    // 4. 如何接消息
    ws.onmessage = (event) => {
      console.log('服务端发的消息：',event)
    }
    // 5. 如何关闭
    document.querySelector('#btn2').addEventListener('click', () => {
      ws.close()
    })
    // 6. 监听通信关闭
    ws.onclose = () => {
      console.log('连接关闭')
    }
  </script>
</body>
</html>